An over-the-counter drug commonly used to treat allergies may one day also contribute to the treatment of hepatitis C, according to new research in mice published in the journal Science Translational Medicine.

For the last 10 years, researchers at the National Institutes of Health (NIH) and Hiroshima University have been searching for new, better drugs to treat hepatitis C, an infectious disease that attacks the liver. By screening thousands of drug compounds in a U.S. Food and Drug Administration library—many of which are already approved and on the market—the researchers have determined that a class of antihistamines may be repurposed to treat hepatitis C. The drug chlorcyclizine HCI (CCZ)—a drug that’s been approved since the 1940s—was shown to be the most promising inhibitor of the virus, the new research found.

“Current drugs against hepatitis C, although they are effective, are expensive, have side effects, and are associated with drug resistance,” says study author Dr. T. Jake Liang, a senior investigator of liver disease at NIH. “There’s definitely unmet needs in the current regime of treatment.”